I am studying for a test and this is a practice question. I cannot figure it out for the life of me. Any assistance would be greatly appreciated.

When Ben Taylor was born, his parents began depositing $500 at the beginning of every year into an annuity to save for his college education. If the account paid 7% interest compounded annually for the first 10 years and then dropped to 5% for the next 8 years, how much is the account worth now that Ben is 18 years old and ready for college?